Mass polymerization process in the presence of an alkylated phenoxypoly (alkyleneoxy)alkanol



United States Patent MASS PQLYMERIZATIQN PROCESS IN THE PRES- ENCE 6F AN ALKYLATED PHENOXYPOLY(AL- KYLENEOXY)ALKANOL Alva F. Harris, Wiibralram, Mass, assignor to Monsanto Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Oct. 21, 1965, Ser. No. 500,307

13 Claims. (Cl. 260-880) ABSTRACT OF THE DESCLGSURE There is disclosed a mass polymerization process for monovinylidene aromatic hydrocarbons wherein there is incorporated in the polymerizable mixture an alkylated phenoxypoly(alkyleneoxy) alkanol after which the mixture is heated to produce polymerization of the monomers and thereafter the polymerized formulation is separated from the reaction vessel.

The present invention relates to a novel process for the mass polymerization of styrene-type monomers.

It is well known that styrene-type monomers can be mass polymerized thermally or catalytically to prepare polymers having molecular weights and residual monomer contents which vary with certain reaction parameters; e.g., the catalyst concentration, the time and temperature of the reaction, etc. It is also known that the product of the mass polymerization process may have a undesirably high residual monomer content when the parameters of the process are controlled so as to prepare a moldinggrade polystyrene; i.e., a polystyrene having a Staudinger average molecular weight in the range of 40,000 to 100,000.

As shown in the United States Patent No. 2,675,362, certain catalysts make it possible to use a mass polymerization process to prepare molding-grade polystyrene having a residual monomer content as low as 0.35 to 0.5 percent and the product has improved physical and molding properties because of the reduction in residual monomer content. Accordingly, it has been considered desirable to find and employ a catalyst capable of reducing the residual monomer content to even lower levels without otherwise causing degradation of the product because of the advantages which might be obtained thereby. Accordingly, it has been suggested to employ a catalyst system containing an organoperoxysilane in United States application for Letters Patent Ser. No. 385,061, filed July 24, 1964, and entitled Polymerization Process granted on J an. 10, 1967 as United States Patent No. 3,297,669.

In one type of mass polymerization process, the monomers are initially polymerized in a kettle or reaction vessel over a relatively low temperature range on the order of 125 to 75 centigrade to a conversion on the order of about 15.0 to 45.0 percent. Thereafter, the partially polymerized mass is transferred to a platen and frame-type press wherein the temperature thereof is gradually raised to about 180 to 200 centigrade over a period of three to seven hours, and is finally heated at about 180 to 200 centigrade for about one to five hours to complete the reaction. After polymerization has been completed, the polymer is cooled to about 30 to 70 centigrade, and the platens are removed and the cakes of polymer extracted from the frames. Exemplary of such presses are those disclosed in United States Patent No. 2,067,580, granted Jan. 12, 1937, to Otto ROllIn; and United States Patent No. 3,140,917, granted July 14, 1964, to Max Klein.

It is an object of the present invention to provide a novel process for mass polymerizing styrene-type monomers wherein a platen and frame-type press is utilized and wherein separation of the polymerized mass from the ice platen and frames of the press is facilitated and maintenance of the press is reduced.

Another object is to provide a novel mass polymerization process utilizing an organoperoxysilane catalyst to provide a polymer with low residual monomer content.

Other objects and advantages will be readily apparent from the following detailed specification and claims.

It has now been found that the foregoing and related objects can be readily attained in a process wherein a monovinyl aromatic monomer selected from the group consisting of a monovinylidene aromatic hydrocarbon and ar-halo monovinylidene aromatic hydrocarbon and mixtures thereof is admixed with 0.05 to 1.0 percent by weight, based upon the total weight of the admixture, of an alkylated phenoxypoly(alkyleneoxy)alkanol, and the monomer is thereafter polymerized, in mass, by heat and a catalyst. In accordance with one aspect of the process, the admixture is initially partially polymerized at a temperature of about to 125 centigrade to effect conversion of about 15.0 to 45.0 percent of the monomer. This initially partially polymerized admixture is then transferred to a platen and frame-type press wherein it is subjected to increasing temperature and gradually raised to about 180 to 200 centigrade, after which it is maintained at a temperature of about 180 to 200 centigrade to effect substantially complete conversion of the monomer. The polymerization product is then cooled to a temperature of 20 to 70 centigrade while in the press, and the press is then opened. The platens are removed, and the cakes of polymerization product are extracted from the individual frames of the press.

In accordance with the preferred aspect of the present invention, the catalyst employed is an organoperoxysilane having a half life of about 220 to 30,000 hours in benzene at centigrade, and the admixture is initially heated at 75 to centigrade until 15.0 to 45.0 percent conversion to polymer is obtained, the temperature being so regulated as to be in the 75 to 95 centigrade range when this conversion is obtained. Thereafter, the reaction temperature of the admixture is gradually raised to to 200 centigrade over a period of about three to seven hours and maintained at 180 to 200 centigrade for about one-half to five hours to effect substantially complete conversion of the monomer.

THE ALKYL PHENOL-ALKYLENE OXIDE CONDENSATE The alkylated phenoxypoly(alkyleneoxy)alkanols have a structural formula as follows:

wherein R is an alkyl group containing eight to twelve carbon atoms, R and R" are hydrogen, methyl or ethyl groups and together provide not more than two carbon atoms, and n is 4 to 75.

As is well known in the art, such compounds are produced by condensing an alkylene oxide or mixtures of alkylene oxides with an alkylphenol. The preferred compositions are alkylated phenoxy polyethyleneoxy ethanols, although mixed condensates of ethylene oxide and propylene oxide may be highly advantageous. Exemplary of such compositions are nonylphenol-ethylene oxide condensates, tridecylphenol-ethylene oxide condensates, octylphenol-ethylene oxide condensates, dodecylphenolethylene oxide condensates, nonylphenol-propylene oxide condensates, nonylphenol (ethyleneoxy propyleneoxy) mixed condensates, etc.

Although this component may be added in the amount of 0.05 to 1.0 percent by weight of the monomer admixture with beneficial effect, it is preferably employed in the range of 0.1 to 0.4 pescent by weight due to considerations of optimum efficiency, ease of handling and economics. Generally, the component is readily admixed directly with the monomer, although it may be added as a solution or dispersion in another component if so desired to minimize separate additions.

From the standpoint of obtaininr optimum compositions when utilizing an organoperoxysilane catalyst, nonylphenol-ethylene oxide condensates having a molar ratio of l:3050 have been found highly advantageous in that they minimize the deleterious effect of residual moisture in the monomer at low temperature polymerization on the order of 90 to 100 centigrade thus conserving the catalyst for its optimum utilization at high temperatures of 180 to 200 centigrade. Generally the nonylphenol-ethylene oxide condensates having a reverse ratio of 3050:1 have proven highly advantageous for use of various catalyst systems because of their generally outstanding performance.

MGNO-MERS The present invention is applicable to the polymerization of polymerizable monomers comprising a monovinylidene aromatic hydrocarbon and/or an ar-halo monovinylidene aromatic hydrocarbon, e.g., styrene; vinyl naphthalene; ar-alkylstyrenes, such as mand p-methylstyrenes, ar-ethylstyrenes, p-t-butylstyrene, etc.; ar-halostyrenes, such as o-chlorostyrene, p-bromostyrene, 2-chloro-4-methylstyrene, etc. :and mixtures thereof. The monovinylidene aromatic monomer may constitute the only component of the polymerizable material or may be in admixture with one or more copolymerizable monomers, such as acrylonitrile; methacrylonitrile; an alkyl methacrylate, e.g., the methyl, ethyl, propyl, and butyl methacsylates; the corresponding alkyl acrylates; alphaalkylstyrenes, e.g., alpha-methylstyrene, alpha-ethylstyrene, alpha-methyl-p-methylstyrene, etc. Ordinarily, the monovinylidene aromatic monomer constitutes at least 50.0 percent by weight of the polymerizable material.

\Vhen desired, the polymerizable material can have a rubbery conjugated, 1,3-diene polymer (e.g., natural rubber, polybutadiene, polyisopsene, copolymers of butadiene and/or isoprene with lesser amounts of comonomers such as styrene, acrylonitrile, methyl methacrylate, etc.) dissolved therein, ordinarily in concentrations of 1.0 to 25.0 percent, based on the weight of polymerizable material. Also, the reaction mixture can contain other optional ingredients, e.g., plasticizess and stabilizers, etc.

CATALYSTS The present invention is applicable to various types of catalyst systems useful in polymerizing the monomers such as the conventional monomer-soluble peroxy compounds having a half life of to 15,000 hours in benzene at 100 centigrade. Utilizable peroxy compounds include, e.g., hydrogen peroxide, di-t-butyl diperphthalate, t-butyl peracetate, t-butyl perbenzoate, dicumyl peroxide, di-tbutyl peroxide, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5 -dimethyl-2,5 -di- (t-butyiperoxy)hexyne-3, t-butyl hydroperoxide, cumene hydroperoxide, p-menth'ane hydroperoxide, cyclopentane hydroperoxide, diisopropylbenzene hydroperoxide, p-t-butylcuinene hydroperoxide, pinane hydroperoxide, 2,5-dimethylhexane-Z,S-dihydroperoxide, etc., and mixtures thereof.

However, the preferred catalyst systems of the present invention are those utilizing an organoperoxysilane to provide high temperature catalytic activity so as to reduce the residual monomer content to a relatively low level. The organoperoxysilanes can be any monomer-soluble organoperoxysilane having a half life of about 220 to 30,000 hours in benzene at 100 centigrade, but the organoperoxysilanes having half lives in benzene of about 500 to 30,000 hours, pasticularly 8000 to 28,000 hours,

are preferred. Organoperoxysilanes having half lives substantially shorter than about 220 hours in benzene at centigrade are not advantageous in the practice of the invention because they are completely or substantially completely consumed before the reaction reaches the finishing stage, i.e., the stage conducted at to 200 centigrade, then the presence of a catalyst is required in order to reduce residual monomer content. Organoperoxysilanes having half lives longer than about 30,000 hours in benzene at 100 centigrade are at least less efiicient and are completely ineffective when they are too stable to decompose at temperatures of 180 to 200 centigrade.

Although trimethylsilylperoxytrimethylsilane and other organoperoxysilanes containing more than one silicon atom and having suitable half lives can be employed, the preferred organoperoxysilanes are compounds corresponding to the formula:

wherein R R and R are independently selected from the group consisting of alkyl, cycloalkyl, aryl and aralkyl radicals and R R and R are independently selected from the group consisting of alkyl, cycloalkyl, aryl and aralkyl radicals and R R and R are independently selected from the group consisting of :alkyl, cycloalkyl, aryl and ar-alkyl radicals and a radical corresponding to the formula:

wherein R R and R are independently selected from the group consisting of alkyl, cycloalkyl, aryl and aralkyl radicals. Exemplary of the allcyl, cycloalkyl, aryl and aralkyl radicals which can be present in these compounds are methyl, ethyl, propyl, butyl, pentyl, hexyl, cyelobutyl, cyclopentyl, cyclohexyl, menthyl, phenyl, tolyl, naphthyl, benzyl, etc. The preferred compounds are those in which the alltyl and cycloalkyl radicals contain up to 6 carbon atoms and the aryl and aralkyl radicals contain up to 12 carbon atoms.

Such compounds, when not commercially available, can be prepared by reacting a suitable halosilane (e.g., diethyldifluorosilane, ethyltrifluorosilane, tetrafluorosilane, trimethyl chlorosilane, triphenylchlorosilane, ditolyldichlorosilane, naphthyltrifluorosilane, dicyclohexyldichlorosilane, benzyltrichlorosilane, ethylisobutylbenzylchlorosilane, etc.) with a suitable organic hydroperoxide or mixture of organic hydroperoxides in the presence of a hydrogen halide acceptor such as ammonia or an amine in a solvent such as ether, etc., essentially in accordance with the equation:

wherein X represents a halogen, (i.e. F, Cl, Br, or I), R and R represent alkyl, cycloalkyl, aryl, or aralkyl radicals, and n is an integer of 1 t0 4.

Exemplary of the organoperoxysilanes which can be employed are t-butylperoxytrimethylsilane, di(t-butylperoxy)dirnethylsilane, tri(t-butylperoxy)methylsilane, tetra- (t-butylperoxy)silane, di(t-butylperoxy)methylphenylsilane, di(t-butylperoxy)diphenylsilane, tn'(t-butylperoxy)- phenylsilane, t-butylperoxytriethylsilane, di(t-butylperoxy)diethylsilane, tri(t-butylperoxy)benzylsilane, tri(tbutylperoxy)naphthylsilane, tri(t-butylperoxy)cyclohexylsilane, t-amylperoxytrimethylsilane, Z-phenyl-Z-propylperoxytrimethylsilane, p-methylperoxytIimethylsilane, etc., and mixtures thereof.

The amount of organoperoxysilane employed varies with the particular product desired but is ordinarily in the range of about 0.001 to 0.1 percent, based on the weight of the polymerizable material. The lower concentrations of silane, e.g., about 0.001 to 0.04 percent, are usually employed when a co-catalyst is used; the higher concentrations of silane, e.g., about 0.04 to 0.1 percent are usually employed when no co-catalyst is used.

In many instances, it is desirable to employ the organoperoxysilane in combination with a conventional peroxy catalyst because of the catalytic effectiveness of such peroxy compounds at the temperatures employed prior to the finishing stage of the reaction, i.e., at the temperatures of 75 to 180 centigrade. When included as a catalyst component, in such a combined catalyst system, the peroxy compound is usually employed in concentrations of 0.01 to 0.1 percent by weight of the monomer, and preferably about 0.01 to 0.05 percent by weight.

POLYMERIZATION PROCESS The monomers are initially polymerized in a kettle or reaction vessel over a relatively low temperature range on the order of 125 to 75 centigrade to obtain conversion of the monomer to the extent of about 15 to 45 percent. Thereafter, the partially polymerized mass is heated so as to gradually raise the temperature thereof to about 180 to 200 centigrade over a period of three to seven hours, after which it is finally heated at a temperature of about 180 to 200 centigrade for about one to five hours to complete the polymerization reaction.

In accordance with the preferred aspect of the present invention, the partially polymerized mass is transferred to a platen and frame-type press where the temperature is elevated and the final polymerization conducted. After the polymerization has been completed, coolant is supplied to the press to cool the polymer to a temperature of about 30 to 70 centigrade, the platens are removed and the cakes of polymer extracted from the frames.

When using a catalyst composition according to the preferred process wherein organoperoxysilanes are included, a fairly specific time-temperature cycle is utilized. In the first stage of the reaction, polymerization is conducted at 75 to 125 centigrade for about six to twentyfour hours until 15.0 to 45.0 percent of the monomer has been converted to polymer; in the second stage, the reaction temperature is gradually raised from 75 to 95 centigrade to 180 to 200 centigrade over a period of about three to seven hours; in the final stage, the reaction temperature is maintained at 180 to 200 centigrade for about one-half to five hours.

The manner of manipulating the reaction temperature during the first stage of the reaction in order to be in the 75 to 95 centigrade range for the beginning of the second stage of the reaction is not critical, e.g., an initial temperature of about 100 to 125 centigrade can be gradually lowered to 75 to 95 centigrade during the first stage of the reaction or the temperature can be maintained at 75 to 95 centigrade throughout the first stage of the reaction, etc. According to a preferred embodiment, the reaction mixture is initially heated to 105 to 115 centigrade and the temperature gradually lowered to about 90 centigrade until about 25.0 to 45.0 percent conversion to polymer is obtained, after which the temperature is gradually raised to 180 to 200 centigrade over a period of about three to seven hours and then maintained at 1 80 to 200 centigrade for about one to five hours to complete the reaction. Especially good results are also obtained by initially heating the reaction mixture at 90 centigrade to about 25 to 35 percent conversion, then heating at a temperature gradually raised to 180 to 200 centigrade over a period of about four to five hours, and finally heating at 180 to 200 centigrade for one to four hours.

In utilizing the organoperoxysilane, it has been noted that the catalyst is susceptible to attack by residual moisture in the monomer. However, the preferred alkylated phenoxypoly(alkyleneoxy)alkanols of the present invention have been noted to reduce the susceptibility to moisture at temperatures on the order of to 100 centigrade so as to avoid premature reaction of this high-temperature catalyst. In any event, excessive moisture content in the monomer is to be avoided when utilizing such catalysts to ensure optimum efiicacy.

The polymer produced by the present invention is found to release readily from the frames of the press and to subsequently exhibit self-lubricating properties in molding operations. In addition to providing low maintenance upon the polymerization equipment, the more facile operation and utilization of this type polymerization process enhances the economics thereof.

Illustrative of the efficacy of the present invention are the following specific examples in which all parts are parts by weight.

Example 1 PART A.CONTROL In 100 parts of styrene were dissolved 0.04 part of di-t butyl peroxide and 0.01 part dimethyl di(t-butyl peroxy)silane. The reaction vessel was purged with nitro gen and heated by a fluid at a temperature of about 90 to centigrade for about twenty hours to convert about 30.0 percent of the styrene to polymer. The partially polymerized mass was then gradually raised in temperaature by a heating fluid which has its temperature increased from about 90 centigrade to about 180 centigrade over a period of about six and one-half hours in a platen and frame type press. Thereafter, the heating fluid was held .at about 180 centigrade for two hours to complete polymerization. The press was then cooled to about 30 centigrade and opened. The platens were separated from the cakes of polymer and the cakes extracted from the frames.

It was noted that the cakes adhered to the platens and to the frames making separation difiicult and also that the platens had a white film of polymer remaining thereon after separation requiring cleaning of these surfaces.

The polymer product had a Staudinger average molecular weight of about 65,000 and a residual monomer content of 0.29 percent by weight.

PART B A product was prepared by substantially repeating Part A and including in the monomer formulation 0.2 part nonylphenolethylene oxide condensate (molar ratio 1:10)

It was noted that the polymer cakes produced by this formulation separated readily from the platens and frames which evidenced no residual film of polymer thereon. The cakes had glossy surfaces and the polymer was free from haze and color.

The polymer product had a Staudinger average molecular Weight of about 65,000 and a residual monomer content of 0.13 percent by weight, thus evidencing a reduction in residual monomer content.

Example 2 In parts of styrene were dissolved 0.04 part of di-tbutylperoxide, 0.01 part of dimethyl-di-(t-butyl peroxy)silane and 0.2 part of nonylphenol-ethylene oxide condensate (1:20 molar ratio). The reaction vessel was purged with nitrogen and heated by a fluid at a temperature of about 90 centigrade for about twenty hours to convert about 30.0 percent of the styrene to polymer. The partially polymerized mass was then gradually raised in temperature by a heating fluid which had its temperature increased from about 90 centigrade to about centigrade over a period of about six and one-half hours in a platen and frame type press. Thereafter, the heating fluid was held at about 180 centigrade for about two hours to complete polymerization. The press was then cooled to about 30 centigrade and opened. The platens were separated from the cakes of polymer and the cakes extracted from the frames.

frames are thereafter separated from the polymerization product.

6. The process of claim 4 wherein said catalyst includes an organoperoxysilane having a half life of about 220 to 30,000 hours in benzene at 100 centigrade.

7. The process of claim 3 wherein the organoperoxysilane is a compound corresponding to the formula:

wherein R R and R are independently selected from the group consisting of alkyl, cycloalkyl, aryl and aralkyl radicals and R R and R are independently selected from the group consisting of alkyl, cycloalkyl, aryl, and aralkyl radicals and a radical corresponding to the formula:

wherein R R and R are independently selected from the group consisting of alkyl, cycloalkyl, aryl and aralkyl radicals.

8. The process of claim 1 wherein the polymerizable material is styrene.

9. The process of claim 1 wherein the polymerizable material is styrene-acrylonitrile.

10. The process of claim 1 wherein the polymerizable material contains a dissolved rubbery conjugated 1,3- diene polymer.

11. A mass polymerization process which comprises (1) forming a reaction mixture by dissolving in a polymerizable material comprising at least 5 percent by weight of a monovinylidene aromatic monomer of the group consisting of a monovinylidene aromatic hydrocarbon, an ar-halo monovinylidene aromatic hydrocarbon, and mixtures thereof, a monomer-soluble free radical catalyst including an organoperoxysilane corresponding to the formula:

wherein R R and R are independently selected from the group consisting of alkyl, cycloalkyl, aryl and aralkyl radicals and R R and R are independently selected 10 from the group consisting of alkyl, cycloalkyl, aryl and aralkyl radicals and a radical corresponding to the formula:

R7 Rs(:J-O-O wherein R R and R are independently selected from the group consisting of alkyl, cycloalkyl, aryl and aralkyl radicals and 0.05 to 1.0 percent by Weight, based upon the total weight of the reaction mixture, of an alkylated phenoxypoly(alkyleneoxy) alkanol corresponding to the following formula:

wherein R is an alkyl group containing eight to twelve carbon atoms, R and R are hydrogen, methyl or ethyl groups and together provide not more than two carbon atoms, and n is 4 to (2) heating the reaction mixture at about 75 to centigrade to effect conversation of about 15.0 to 45.0 percent of the monomer; (3) transferring the partially converted monomer to a platen and frame type press; (4) heating the reaction mixture in the platen and frame type press with a fluid having a temperature gradually raised to about to 200 centigrade over a period of about three to seven hours; (5) heating the reaction mixture in the press with a fluid having a temperature of about 180 to 200 centigrade for a period of about one to five hours to complete the polymerization reaction and form a polymerization product; (6) cooling the platen and frame press and polymerization product; and (7) thereafter separating the platens and frames from the polymerization product.

12. The process of claim 11 wherein the alkylated phenoxypoly( alkyleneoxy) alkanol is a nonylphenol-ethylene oxide condensate having a molar ratio of 1:30-75.

13. The process of claim 11 wherein said organoperoxysilane is di-(t-butylperoxy)dimethylsilane.

References Cited UNITED STATES PATENTS 3,297,669 1/1967 Harris et al 260880 JOSEPH L. SCHOFER, Primary Examiner.

H. WONG, Assistant Examiner. 

